Cancer cells differentiate, as do normal cells. The tumor cell populations include a relatively small cohort of less differentiated, self-renewing, tumor initiating stem cells and a relatively larger cohort of more differentiated tumor cells. More differentiated cells are more susceptible to chemotherapy and the minor fraction of less differentiated cancer stem cells are more drug resistant, thus contributing to drug refractory relapse. CD133 is an established marker for cancer stem cells
Human CD133 is a cell surface glycoprotein that has been used as a marker of hematopoietic stem cells, neural stem cells, and for enrichment of a tumor initiating cell population in many cancers including colon carcinoma and glioblastoma (Kemper et al.; Weigmann et al., 1997; Yin et al., 1997). Anti-CD133 antibodies are important tools useful in the identification, isolation and targeting of these stem cell populations. Although many CD133 antibodies are commercially available, they have several limitations. First, the most widely used anti-CD133 monoclonal antibodies recognize what was initially thought to be poorly-defined glycosylated epitopes (Bidlingmaier et al., 2008), but more recently reported to be non-glycosylated epitopes that are lost during differentiation, perhaps due to epitope masking (Kemper et al.). In either case, these antibodies do not detect cells expressing certain post-translationally modified CD133 epitopes and therefore cannot be used to determine the total CD133 expression. Second, commercially available anti-CD133 antibodies that target an unmodified CD133 epitope are often polyclonal. Third, most of the currently available antibodies are only suitable for use in limited biological assays. To overcome these shortcomings, there is a need to generate a new anti-CD133 monoclonal antibody that specifically recognizes a non-glycosylated epitope of CD133 and is useful in multiple biological assays.
Carcinomas are invasive malignant tumors of transformed epithelial cells. Some of the deadliest cancers are carcinomas including drug refractory cancers of the pancreas, head and neck, prostate, breast, colon, and other organs. For example, in pancreatic cancer, only 10-15% of patients are found to be resectible at diagnosis because of its aggressive growth and rapid speed of metastasis to lymph nodes and liver. Median survival is 3-6 months with a 5-year survival rate of 1-4% when all stages are considered and more than 32,000 patients each year die in U.S. alone. Breast cancer, with a considerably better survival rate, still had an estimated 178,000 new cases in 2007 with an expected 40,000 fatalities according to the American Cancer Society. In the case of head and neck cancers, in the United States, of 40,000 in reported cases in 2006, about 11,000 died of their disease. The primary culprit is a metastatic reoccurrence of drug refractory disease, so alternative drugs are urgently needed.